An excellent novel about the Iraq War and its homefront fallout has been turned into a rather flat and disappointing film in The Yellow Birds. Principally the story of two working-class privates and how the death of one of them produces waves of incalculable trauma and incomprehension among his survivors, the story has been skewed significantly from the book to concentrate more on those left behind, a puzzling move in that it lessens the tale’s structural power and aching ambiguity. Critical support from enthusiasts of director Alexandre Moors’ previous feature, the 2013 Sundance entry Blue Caprice, doubtless will launch this into further festival play and specialized release, which will be further boosted by the presence of two excellent up-and-coming actors, Alden Ehrenreich and Tye Sheridan.

Written by an Iraq War combat veteran, Kevin Powers' short, widely acclaimed novel is notable for its unflinching realism as well as its Hemingway-esque terseness and precision. It also employs a back-and-forth structure, alternating between the wartime past and the Virginia present that only come together at the very end.

While retaining the twin-tracked narrative, screenwriters David Lowery and R.F.I. Porto have reassembled the tale oddly to tilt it far more toward the forlorn domestic consequences triggered by the young men’s fates overseas. They also invented a four-part structure marked by chapter heads — Deployment, Homecoming, Retreat, Surrender — that seem beside the point given the ping-ponging scenario.

All this significantly lessens the sense of forward movement and gradual revelation the story has to offer, while also focusing, quite frankly, on the duller and more predictable behavior of the two principal soldiers’ mothers rather than on the utterly unpredictable and shocking events of wartime.

Moors’ debut with Blue Caprice, which took a curious sidelong look at a real-life Washington, D.C.-area serial killer and his young acolyte, provides fair warning that the director would not take a conventional Hollywood approach to Iraq. In fact, commentary on the war itself remains implicit, with explicit politics drained from both the book and film to let the domestic consequences on display speak acutely for themselves.

Scarcely out of high school, Bartle (Ehrenreich, oddly billed second although his is very much the central character) and Murph (Tye Sheridan) become buddies at Army training camp. The younger Murph is still half boy and couldn’t have a sweeter disposition, which is presumably what inspires Bartle, who is distinctive for not seeming to have an opinion or point of view about anything, to promise Murph’s mother (Jennifer Aniston) that he’ll look after her son, as does the company’s drill sergeant (Jack Huston).

Once the boy-men touch down in the desert, things inevitably pick up a bit. As in the book, there is no sense of overall mission, of bad guys versus good guys, of what the geo-political objectives are. There’s no referencing of Bush or Saddam, no speechifying about what a victory would mean for the world or any of the combatants, or anything else that relates the men’s sacrifices to anything specific, a plus that makes their fates seem all the more arbitrary.

Shooting in Morocco, Moors proves most effective in crafting scenes in which violence erupts out of nowhere. The shoot-outs mainly take place in cities or on their fringes, with the rag-tag enemy fighters popping out of dilapidated structures in ruined areas to do damage before almost inevitably being nailed themselves by the far better equipped Americans. The war scenes are strong, with an emphasis on the almost complete arbitrariness of who lives and dies.

Except we know who will live and die based on the parallel narratives of the young men’s parents, most importantly Aniston’s Maureen Murphy, who gets, on balance, an inordinate amount of screen time trying to pursue the truth about what happened to her unfortunate son.

Then there’s Bartle’s poor white trash mom Amy (Toni Collette), a woman distraught about her returned son’s aimless life once he’s back. No matter the talents of the actresses playing the mothers, what they’re asked to do is strictly one-note stuff dramatically, so little is gained by having them enact so many repetitive scenes.

What may remain unclear to viewers who haven’t read the book are the particulars of Bartle’s fate. Once back in the U.S., he’s pursued at length by an army legal representative (Jason Patric), but what triggers this — something unfortunate though clear on the page — seems vague in this telling.

What Moors does effectively achieve is a mood of enveloping sadness, of lives wasted, of unfulfilled people exhausting themselves in pointless pursuits. Nor is there any sense of life, or its possibilities, outside the narrow worlds in which these characters live.

Ehrenreich and Sheridan make for two very attractive leads but their characters, like the adults, are not provided a full palette of human traits to play with.

The backgrounds are vivid, with Moroccan locations standing in quite nicely for Iraq.